Repeated Administration of the Cannabinoid WIN Alters the Isoflurane-Sparing Effect of Morphine and Dexmedetomidine.

Unlabelled: The impacts of morphine and dexmedetomidine on the MAC of isoflurane were studied in rats constantly medicated with the cannabinoid WIN 55,212-2.

Methods: Prior to the administration of morphine, the MAC was measured in both untreated rats (MAC ) and those treated with a cannabinoid (MAC ). The effects of morphine (MAC ) and dexmedetomidine (MAC ) on untreated rats and rats treated for 21 days with the cannabinoids (MAC ) and (MAC ) were also studied.

Results: MAC was 1.32 ± 0.06, and MAC was 1.69 ± 0.09. MAC was 0.97 ± 0.02 (26% less than MAC ). MAC was 1.55 ± 0.08 (8% less than MAC ), MAC was 0.68 ± 0.10 (48% less than MAC ), and MAC was 0.67 ± 0.08 (60% less than MAC ).

Conclusions: Medication with a cannabinoid for 21 days augmented the MAC of isoflurane. The sparing effect of morphine on isoflurane is lower in rats constantly medicated with a cannabinoid. The sparing effect of dexmedetomidine on the minimum alveolar concentration of isoflurane is greater in rats repeatedly medicated with a cannabinoid.